It’s a first-time homebuyer’s dream: Snag a rundown house in a terrific neighborhood, and then revamp it to your heart’s content.

But fair warning, that fixer-upper could become your worst nightmare.

“You have to really know what you’re getting into,” says Zillow.com real estate expert Brendon DeSimone. “It could be the case where it seems like a good price and then you dig deeper and find that the windows are off, the electrical foundation is messy, and so on.”